1. Field of the Invention
The present invention relates generally to focus adjusting mechanisms and, more particularly, to a focus adjusting mechanism for use in a portable electronic device.
2. Description of Related Art
With the development of technology, portable electronic devices for imaging such as digital cameras and mobile phones with lens modules have all entered widespread use. The lens module is equipped with a focus adjusting mechanism used to capture images of objects with different distances.
A typical focus adjusting mechanism for a lens module 100 is shown in FIG. 1. The lens module 100 includes a lens barrel 10 and a lens barrel holder 12. The lens barrel holder 12 includes a first barrel portion 122 and a second barrel portion 124. The first barrel portion 122 defines an open end 1222, and further defines a screw hole 1226 through the open end 1222. The second barrel portion 124 has a plate 1242 formed therein. The focus adjusting mechanism includes a screw 16 and a spring 18. When assembled, the lens barrel 10 engages into the first barrel portion 122, and can move relative to the first barrel portion 122. The screw 16 engages through the screw hole 1226 to resist one end of the lens barrel 10. The spring 18 is held between the lens barrel 10 and the plate 1242, resisting the other end of the lens barrel 10. In use, the screw 16 is operated to enable the lens barrel 10 to move axially relative to the lens barrel holder 12.
The above focus adjusting mechanism can precisely adjust the focal length of the lens module 100. However, the spring 18 of the focus adjusting mechanism has a relatively short service-life. In addition, when the spring 18 doesn't work, the precise adjustment of the focus adjusting mechanism may be disenabled, and while operating the screw 16 manually, incident light may be blocked.
What is needed, therefore, is a focus adjusting mechanism that can overcome the above-mentioned shortcomings.